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Echo made easy 3rd edition

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Echo made easy 3rd

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Echo made easy 3rd edition

  1. 1. EchoEchoEchoEchoEcho MaMaMaMaMade Eade Eade Eade Eade Easysysysysy®®®®® www.cambodiamed.blogspot.com
  2. 2. Atul Luthra MBBS MD DNB Diplomate National Board of Medicine Physician and Cardiologist New Delhi, India www.atulluthra.in atulluthra@sify.com JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTD New Delhi • Panama City • London • Dhaka • Kathmandu ® EchoEchoEchoEchoEcho MaMaMaMaMade Eade Eade Eade Eade Easysysysysy®®®®® Third Edition
  3. 3. Headquarter Jaypee Brothers Medical Publishers (P) Ltd 4838/24, Ansari Road, Daryaganj New Delhi 110 002, India Phone: +91-11-43574357 Fax: +91-11-43574314 Email: jaypee@jaypeebrothers.com Overseas Offices J.P. Medical Ltd., 83 Victoria Street London SW1H 0HW (UK) Phone: +44-2031708910 Fax: +02-03-0086180 Email: info@jpmedpub.com Jaypee Brothers Medical Publishers (P) Ltd 17/1-B Babar Road, Block-B Shaymali, Mohammadpur Dhaka-1207, Bangladesh Mobile: +08801912003485 Email: jaypeedhaka@gmail.com Jaypee-Highlights Medical Publishers Inc. City of Knowledge, Bld. 237, Clayton Panama City, Panama Phone: +507-301-0496 Fax: +507-301-0499 Email: cservice@jphmedical.com Jaypee Brothers Medical Publishers (P) Ltd Shorakhute Kathmandu, Nepal Phone: +00977-9841528578 Email: jaypee.nepal@gmail.com Jaypee Brothers Medical Publishers (P) Ltd. Website: www.jaypeebrothers.com Website: www.jaypeedigital.com © 2012, Jaypee Brothers Medical Publishers All rights reserved. No part of this book may be reproduced in any form or by any means without the prior permission of the publisher. Inquiries for bulk sales may be solicited at: jaypee@jaypeebrothers.com This book has been published in good faith that the contents provided by the author contained herein are original, and is intended for educational purposes only. While every effort is made to ensure accuracy of information, the publisher and the author specifically disclaim any damage, liability, or loss incurred, directly or indirectly, from the use or application of any of the contents of this work. If not specifically stated, all figures and tables are courtesy of the author. Echo Made Easy® First Edition : 2005 Second Edition : 2007 Third Edition : 2012 ISBN 978-81-8448-939-2 Printed at ®
  4. 4. To My Parents Ms Prem Luthra and Mr Prem Luthra Who guide and bless me from heaven
  5. 5. PrPrPrPrPreface teface teface teface teface to the Thiro the Thiro the Thiro the Thiro the Third Editiond Editiond Editiond Editiond Edition Ever since the second edition of Echo Made Easy was published five years back, there have been tremendous advancements in the field of echocardiography. To name a few, three- dimensional technique, tissue-Doppler study and myocardial- contrast imaging have gained considerable popularity. Nevertheless, there remains an unmet need for a simplistic book on basic echocardiography for the uninitiated reader. It gives me immense pleasure to present to cardiology students, resident doctors, nurses and technicians working in cardiology units, this vastly improved third edition of Echo Made Easy. The initial chapters will help the readers to understand the principles of conventional echo and color-Doppler imaging, the various echo-windows and the normal views of cardiac structures. The abnormalities observed in different forms of heart disease including congenital, valvular, coronary, hypertensive, myocardial, endocardial and pericardial diseases have been discussed under separate sections. Due emphasis has been laid on diagnostic pitfalls, differential diagnosis, causative factors and clinical significance. Those who have read the previous editions of Echo Made Easy will definitely notice a remarkable improvement in the layout of the book. Readers will appreciate a bewildering array of striking figures and impressive tables. For this, I am extremely grateful to Dr Rakesh Gupta, an expert in echocardiography of international repute. He has been very kind and generous in providing me with real-time images from his vast and valuable
  6. 6. Echo Made Easyviii collection. I am also very thankful to M/s Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India, who infuse life into subsequent editions of all my books, by virtue of their typesetting and artwork expertise. Do keep pouring with your comments and criticism. Bouquets and brickbats are both welcome. Bon voyage through Echo Made Easy, third edition. Atul Luthra
  7. 7. PrPrPrPrPreface teface teface teface teface to the Fo the Fo the Fo the Fo the Fiririririrssssst Editiont Editiont Editiont Editiont Edition Ultrasound has revolutionized clinical practice by providing the fifth dimension to physical examination after inspection, palpation, percussion and auscultation. Echocardiography is the application of ultrasound for examining the heart. It is a practi- cally useful, widely available, cost-effective and noninvasive diagnostic tool. Usage of echo is rapidly expanding with more and more clinicians requesting for and interpreting it to solve vexing clinical dilemmas. While I was preparing the manuscript of this book, many a time two questions crossed my mind. First, is such a book really required? And second, am I the right person to write it? At the end of the day, I, somehow, managed to convince myself that a precise and practical account of echocardiography is indeed required and that an academic Physician like myself can do justice to this highly technical subject. The book begins with the basic principles of ultrasound and Doppler and the clinical applications of various echo-modalities including 2-D echo, M-mode scan, Doppler echo and color- flow mapping. This is followed by an account of different echo- windows and normal echo-views along with normal values and dimensions. The echo features of various forms of heart disease such as congenital, valvular, coronary and hypertensive disorders are individually discussed. Due emphasis has been laid on pitfalls in diagnosis, differentiation between seemingly similar findings, their causation and clinical relevance. Under- standably, figures and diagrams can never create the impact of dynamic echo display on the video-screen. Nevertheless, they have been especially created to leave a long-lasting visual
  8. 8. Echo Made Easyx impression on the mind. In keeping with the spirit of simplicity, difficult topics like complex congenital cardiac disease, prosthetic heart valves and transesophageal echocardiography have been purposely excluded. The book is particularly meant for students of cardiology as well as keen established clinicians wanting to know more about echo. If I can coax some Physicians like myself to integrate echocardiography into their day-to-day clinical practice, I will feel genuinely elated for a mission successfully accomplished. Atul Luthra
  9. 9. AcknowledgmentAcknowledgmentAcknowledgmentAcknowledgmentAcknowledgmentsssss I am extremely grateful to: • My school teachers who helped me to acquire good command over English language. • My professors at medical college who taught me the science and art of clinical medicine. • My heart patients whose echo-reports stimulated my gray matter and made me wiser. • Authors of books on echocardiography to which I referred liberally, while preparing the manuscript. • Dr Rakesh Gupta who has been kind and supportive in providing me with excellent images. • My readers whose generous appreciation, candid comments and constructive criticism constantly stimulate me. • M/s Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India, who repose their unflinching faith in me and provide encouragement along with expert editorial assistance.
  10. 10. ContContContContContentententententsssss 1. What is an Echo? 1 • Principles of Ultrasound 1 • Principles of Doppler 6 2. Conventional Echo 15 • Two-dimensional (2-D) Echo 15 • Motion-mode (M-Mode) Echo 17 • Continuous Wave (CW) Doppler 18 • Pulsed Wave (PW) Doppler 19 • Clinical Applications of Echo 20 3. Color Doppler Echo 23 • Principles of Color Doppler 23 • Applications of Color Doppler 28 4. The Echo Windows 33 • Transthoracic Echo 33 • Standard Echo Windows 34 • Transesophageal Echo 43 • Future Directions in Echo 46 5. Normal Views and Values 51 • Echo Interpretation 51 • Scanning Sequence 51 • What is Normal? 53
  11. 11. Echo Made Easyxiv • Normal Variants 53 • Normal Dimensions 55 • Normal Valves 60 6. Ventricular Dysfunction 65 • LV Systolic Dysfunction 65 • LV Diastolic Dysfunction 77 • RV Systolic Dysfunction 83 7. Cardiomyopathies 87 • Dilated Cardiomyopathy 87 • Restrictive Cardiomyopathy 92 • Hypertrophic Cardiomyopathy 96 8. Coronary Artery Disease 103 • Indications for Echo in CAD 103 • Myocardial Ischemia 104 • Myocardial Infarction 105 • Left Ventricular Dysfunction 111 • Right Ventricular Dysfunction 113 • Acute Mitral Regurgitation 114 • Ventricular Septal Defect 116 • Left Ventricular Aneurysm 117 • Ventricular Mural Thrombus 118 • Acute Pericardial Effusion 119 • Coronary Artery Anomalies 119 • Simulating Conditions 120 • Stress Echocardiography 121 9. Systemic Hypertension 125 • Indications for Echo in HTN 125 • Left Ventricular Hypertrophy 125
  12. 12. Contents xv 10. Pulmonary Hypertension 131 • Detection of Pulmonary HTN 131 • Estimation of Pulmonary HTN 134 11. Diseases of Aorta 141 • Sinus of Valsalva Aneurysm 143 • Dilatation of Aorta 144 • Aneurysm of Aorta 145 • Coarctation of Aorta 146 • Dissection of Aorta 148 12. Congenital Diseases 151 • Ventricular Septal Defect 152 • Atrial Septal Defect 154 • Patent Ductus Arteriosus 158 • Tetralogy of Fallot 160 • Eisenmenger Reaction 162 • Quantification of Shunt 162 13. Valvular Diseases 165 • Mitral Stenosis 166 • Mitral Valve Prolapse 176 • Flail Mitral Leaflet 179 • Mitral Annular Calcification 181 • Mitral Regurgitation 183 • Tricuspid Stenosis 191 • Tricuspid Regurgitation 194 • Ebstein Anomaly 200 • Aortic Stenosis 201
  13. 13. Echo Made Easyxvi • Aortic Regurgitation 214 • Pulmonary Stenosis 225 • Pulmonary Regurgitation 228 14. Pericardial Diseases 233 • Pericardial Effusion 233 • Cardiac Tamponade 237 • Constrictive Pericarditis 240 15. Endocardial Diseases 243 • Classification of Endocarditis 243 • Predisposing Cardiac Lesions 244 • Indications for Serial Echoes 245 • Echo Features of Endocarditis 245 16. Intracardiac Masses 253 • Cardiac Tumors 253 • Left Atrial Myxoma 254 • Atrial Thrombus 258 • Ventricular Thrombus 261 17. Thromboembolic Diseases 265 • Indications for Echo in CVA 265 • Thromboembolism in Mitral Stenosis 267 18. Systemic Diseases 269 Index 271
  14. 14. 1 What isWhat isWhat isWhat isWhat is an Echo?an Echo?an Echo?an Echo?an Echo? PRINCIPLES OF ULTRASOUND • Sound is a mechanical disturbance produced by passage of energy through a medium which may be gas, liquid or solid. Every sound has a particular frequency, a wavelength, its own velocity and an intensity. • Sound energy is transmitted through a medium in the form of cycles or waves. Each wave consists of a peak and a trough. The peak coincides with adjacent group of molecules moving towards each other (compression phase). The trough coincides with adjacent group of molecules moving away from each other (rarefaction phase). • Frequency of sound is the number of times per second, sound undergoes a cycle of rise and fall. It is expressed in cycles per second, or hertz (Hz) and multiples thereof. 1 hertz (Hz) = 1 cycle per second 1 kilohertz (KHz) = 103 Hz = 1000 Hz 1 megahertz (MHz) = 106 Hz = 1000000 Hz • Frequency is appreciated by the listener as pitch of sound. • Wavelength is the distance travelled by sound in one cycle of rise and fall. The length of the wave is the distance between two consecutive peaks.
  15. 15. Echo Made Easy2 • Frequency and wavelength are inter-related. Since, sound travels a fixed distance in one second, more the cycles in a second (greater the frequency), shorter is the wavelength (Fig. 1.1). • Therefore, Velocity = Frequency × Wavelength. • Velocity of sound is expressed in meters per second (m/sec) and is determined by the nature of the medium through which sound propagates. In soft tissue, the velocity is 1540 m/sec. • Intensity of sound is nothing but its loudness or amplitude expressed in decibels. Higher the intensity of sound, greater is the distance upto which it is audible. • The normal audible range of sound frequency is 20 Hz to 20 KHz. Sound whose frequency is above what is audible to the human ear (more than 20 KHz) is known as ultrasound. • The technique of using ultrasound to examine the heart is known as echocardiography or simply echo. • Electricity and ultrasound are two different forms of energy that can be transformed from one to the other by special crystals made of ceramic such as barium titanate. • Ultrasound relies on the property of such crystals to transform electrical current of changing voltage into mechanical vibrations or ultrasound waves. This is known as the piezoelectric (pressure-electric) effect (Fig. 1.2). Fig. 1.1: Relationship between frequency and wavelength: A. High frequency, short wavelength B. Low frequency, long wavelength
  16. 16. What is an Echo? 3 • When electrical current is passed through a piezoelectric crystal, the crystal vibrates. This generates ultrasound waves which are transmitted through the body by the transducer which houses several such crystals. • Most of these ultrasound waves are scattered or absorbed by the tissues, without any obvious effect. Only a few waves are reflected back to the transducer and echoed. • Reflected ultrasound waves again distort the piezoelectric crystals and produce an electrical current. These reflected echoes are processed by filtration and amplification, to be eventually displayed on the cathode-ray-tube. • The reflected signal gives information about the depth and nature of the tissue studied. Most of the reflection occurs at interfaces between tissues of different density and hence a different echo-reflectivity. Fig. 1.2: The piezoelectric effect in ultrasound
  17. 17. Echo Made Easy4 • The magnitude of electrical current produced by the reflected ultrasound determines the intensity and brightness on the display screen. • On the gray-scale, high reflectivity (from bone) is white, low reflectivity (from muscle) is gray, and no reflection (from air) is black (Table 1.1). • The location of the image produced by the reflected ultrasound depends upon the time lag between transmission and reflection of ultrasound. • Deeper structures are shown on the lower portion of the display screen while superficial structures are shown on the upper portion. This is because the transducer is at the apex of the triangular image on the screen (Fig. 1.3). • When ultrasound is transmitted through a uniform medium, it maintains its original direction but gets progressively scattered and absorbed. • When ultrasound waves generated by the transducer encounter an interface between tissues of different density and thus different echo-reflectivity, some of the ultrasound waves are reflected back. • It is these reflected ultrasound waves that are detected by the transducer and analyzed by the echo-machine. • The wavelength of sound is the ratio between velocity and frequency (Wavelength = Velocity/Frequency). TABLE 1.1 Echo-reflectivity of various tissues on the gray-scale Tissue Reflectivity Shade Bone High White Muscle Low Gray Air Nil Black
  18. 18. What is an Echo? 5 • Since wavelength and frequency are inversely related, higher the frequency of ultrasound, shorter is the wavelength. Shorter the wavelength, higher is the image resolution and lesser is the penetration. • Therefore, high frequency probes (5.0–7.5 MHz) provide better resolution when applied for superficial structures and in children (Table 1.2). Fig. 1.3: Transducer is at the apex of visual display: A. Right ventricle in the upper screen B. Left ventricle in the lower screen TABLE 1.2 Features and applications of probes having different frequency Frequency Penetration Resolution Study Age (MHz) in tissue of image depth group 2.5–3.5 Good Less Deep Adults 5.0–7.5 Less Good Superficial Children
  19. 19. Echo Made Easy6 • Conversely, lower the frequency of ultrasound, longer is the wavelength. Longer the wavelength, lower is the image resolution and greater is the tissue penetration. • Therefore, low frequency probes (2.5–3.5 MHz) provide better penetration when applied for deeper structures and in adults (Table 1.2). PRINCIPLES OF DOPPLER • The Doppler acoustic effect is present and used by us in everyday life, although we do not realize it. Imagine an automobile sounding the horn and moving towards you, going past you and then away from you. • The pitch of the horn sound is higher when it approaches you (higher frequency) than when it goes away from you (lower frequency). • This means that the nature of sound depends upon the relative motion of the listener and the source of sound. • The change of frequency (Doppler shift) depends upon the speed of the automobile and the original frequency of the horn sound. • Ultrasound reflected back from a tissue interface gives information about the depth and echo-reflectivity of the tissue. On the other hand, Doppler utilizes ultrasound reflected back from moving red blood cells (RBCs). • The Doppler principle is used to derive the velocity of blood flow. Flow velocity is derived from the change of frequency that occurs between transmitted (original) and reflected (observed) ultrasound signal. • The shift of frequency (Doppler shift) is proportional to ratio of velocity of blood to speed of sound and to the original frequency.
  20. 20. What is an Echo? 7 • It is calculated from the following formula: D O V F F C FD : Doppler shift V : Velocity of blood Fo : Original frequency C: Speed of sound Therefore, velocity of blood flow is: D O F C V F Further refinement of this formula is:     D O F C V 2F Cos • The original frequency (Fo) is multiplied by 2 since Doppler shift occurs twice, during forward transmission as well as during backward reflection. • Cosine theta (Cos θ) is applied as a correction for the angle between the ultrasound beam and blood flow. The angle between the beam and flow should be less than 20o to ensure accurate measurement. • Cos θ is 1 if the beam is parallel to blood flow and maximum velocity is observed. Cos θ is 0 if the beam is perpendicular to blood flow and no velocity is detected. • It is noteworthy that for Doppler echo, maximum velocity information is obtained with the ultrasound beam aligned parallel to the direction of blood flow being studied. • This is in sharp contrast to conventional echo, where best image quality is obtained with the ultrasound beam aligned perpendicular to the structure being studied.
  21. 21. Echo Made Easy8 • Since, the original frequency value (2×Fo) is in the denominator of the velocity equation, it is important to remember that maximum velocity information is obtained using a low frequency (2.5 MHz) transducer. • There is a direct relationship between the peak velocity of blood flow through a stenotic valve and the pressure gradient across the valve. • Understandably when the valve orifice is small, blood flow has to accelerate in order to eject the same stroke volume. This increase in velocity is measured by Doppler. • The pressure gradient across the valve can be calculated using the simplified Bernaulli equation: Δ P = 4 V2 P: pressure gradient (in mm Hg) V: peak flow velocity (in m/sec) • This equation is frequently used during Doppler evaluation of stenotic valves, regurgitant lesions and assessment of intracardiac shunts. • The velocity information provided by Doppler complements the anatomical information provided by standard M-mode and 2-D Echo. • Analysis of the returning Doppler signal not only provides information about flow velocity but also flow direction. • By convention, velocities towards the transducer are displayed above the baseline (positive deflection) and velocities away from the transducer are displayed below the baseline (negative deflection) (Fig. 1.4). • The returning Doppler signal is a spectral trace of velocity display on a time axis. The area under curve (AUC) of the spectral trace is known as the flow velocity integral (FVI) of that velocity display.
  22. 22. What is an Echo? 9 • The value of FVI is determined by peak flow velocity and ejection time. It can be calculated by the software of most echo machines. • Careful analysis of the spectral trace of velocity also gives densitometric information. Density relates to the number of RBCs moving at a given velocity. • When blood flow is smooth or laminar, most RBCs travel at the same velocity, since they accelerate and decelerate simultaneously. • The spectral trace then has a thin outline with very few RBCs travelling at other velocities (Figs 1.5A and C). This is known as low variance of velocities. • When blood flow is turbulent as across stenotic valves, there is a wide distribution of RBCs velocities and the Doppler signal appears “filled in” (Fig. 1.5B). This is known as high variance of velocities, “spectral broadening” or “increased band width”. Fig. 1.4: Direction of blood flow and the polarity of deflection: A. Towards the transducer, positive deflection B. Away from transducer, negative deflection
  23. 23. Echo Made Easy10 • It is to be borne in mind that turbulence and spectral broadening are often associated but not synonymous with high flow velocity. • The intensity of the Doppler signal is represented on the gray- scale as darker shades of gray (Fig. 1.6). • Maximum number of RBCs travelling at a particular velocity cast a dark shade on the spectral trace. Few RBCs travelling at a higher velocity cast a light shade. • This is best seen on the Doppler signal from a stenotic valve. The spectral display is most dense near the baseline reflecting most RBCs moving at a low velocity close to the valve (Fig. 1.6A). • Few RBCs accelerating through the stenotic valve are at a high velocity (Fig. 1.6B). • The Doppler echo modes used clinically are continuous wave (CW) Doppler and pulsed wave (PW) Doppler. • In CW Doppler, two piezoelectric crystals are used, one to transmit continuously and the other to receive continuously, without any time gap. • It can measure high velocities but does not discriminate between several adjacent velocity components. Therefore, CW Doppler cannot precisely locate the signal which may Fig. 1.5: Various patterns of blood flow seen on Doppler: A. Laminar flow across a normal aortic valve B. Turbulent flow across stenotic aortic valve C. Normal flow pattern across the mitral valve
  24. 24. What is an Echo? 11 originate from anywhere along the length or breadth of the ultrasound beam. • In PW Doppler, a single piezoelectric crystal to first emits a burst of ultrasound and then receives it after a preset time gap. This time is required in order to switch-over into the receiver mode. • To locate the velocity, a ‘sample volume’ indicated by a small box or circle, is placed over the 2-D image at the region of interest. The ‘sample volume’ can be moved in depth along the path of PW beam indicated as a broken line, until a maximum velocity signal is obtained (Fig. 1.7). • PW Doppler can precisely localize the site of origin of a velocity signal, unlike CW Doppler. • Because of the time delay in receiving the reflected ultrasound signal, PW Doppler cannot accurately detect high velocities exceeding 2 m/sec. Fig. 1.6: Doppler signal across a stenotic aortic valve: A. Most RBCs moving at low velocity B. Few RBCs moving at high velocity
  25. 25. Echo Made Easy12 • However, PW Doppler provides a spectral tracing of better quality than does CW Doppler (Fig. 1.8). • The single crystal of PW Doppler can emit a fresh pulse only after the previous pulse has returned. The time interval between pulse repitition is therefore the sum of the time taken by the transmitted signal to reach the target and the time taken by the returning signal to reach the transducer. Fig. 1.7: Doppler signal from various levels of LV: A. LV apex B. Mid LV C. Sub-aortic Fig. 1.8: Doppler signal from a regurgitant aortic valve showing laminar flow
  26. 26. What is an Echo? 13 • The rate at which pulses are emitted is known as the pulse repetition frequency (PRF). Obviously, greater the depth of interrogation, more is the time interval between pulse repetition and lower is the PRF. • Pulse repetition frequency (PRF) should be greater than twice the velocity being measured. The PRF decreases as the depth of interrogation increases. • The maximum value of Doppler frequency shift that can be accurately measured with a given pulse repetition frequency (PRF) is called the Nyquist limit. • The inability of PW Doppler to detect high-frequency Doppler shifts is known as aliasing. Aliasing occurs when the Nyquist limited is exceeded. • Aliasing is an artificial reversal of velocity and distortion of the reflected signal. The phenomenon of aliasing is also called “wrap around.” • Aliasing can be tackled by one of these modifications: – high pulse repetition frequency – multigate acquisition technique – reduced depth of interrogation – shifting of display baseline.
  27. 27. 2 ConvConvConvConvConventionalentionalentionalentionalentional EchoEchoEchoEchoEcho The modalities of echo used clinically are: I. Image echo • Two-dimensional echo (2-D echo) • Motion-mode echo (M-mode echo). II. Doppler echo • Continuous wave (CW) Doppler • Pulsed wave (PW) Doppler. Different echo modalities are not mutually exclusive but complement each other and are often used together. All of them follow the same principle of ultrasound but differ with respect to the manner in which reflected sound waves are received and displayed. TWO-DIMENSIONAL (2-D) ECHO • Ultrasound reflected from a tissue interface distorts the piezoelectric crystal and generates an electrical signal. The signal produces a dot (spot) on the display screen. • The location of the dot indicates the distance of the structure from the transducer. The brightness of the dot indicates the strength of the returning signal.
  28. 28. Echo Made Easy16 • To create a 2-D image, the ultrasound beam has to be swept across the area of interest. Ultrasound is transmitted along several (90 to 120) scan lines over a wide (45° to 90°) arc and many (20 to 30) times per second. • The superimposition of simultaneously reflected dots, builds up a real-time image on the display screen. Production of images in quick succession creates an anatomical cross-section of structures. Any image frame can be frozen, studied on the screen or printed out on thermal paper or on X-ray film. • 2-D echo is useful to evaluate the anatomy of the heart and the relationship between different structures (Fig. 2.1). • Intracardiac masses and extracardiac pericardial abnor- malities can be noted. The motion of the walls of ventricles and cusps of valves is visualized. • Thickness of ventricular walls and dimensions of chambers can be measured and stroke volume, ejection fraction and cardiac output can be calculated. • 2-D image is also used to place the ‘cursor line’ for M-mode echo and to position the ‘sample volume’ for Doppler echo. Fig. 2.1: Two-dimensional echo (2-D Echo) views: A. Parasternal long-axis (PLAX) view B. Apical four-chamber (A4CH) view
  29. 29. Conventional Echo 17 MOTION-MODE (M-MODE) ECHO • In the M-mode tracing, ultrasound is transmitted and received along only one scan line. • This line is obtained by applying the cursor to the 2-D image and aligning it perpendicular to the structure being studied. The transducer is finely angulated until the cursor line is exactly perpendicular to the image. • M-mode is displayed as a continuous tracing with two axes. The vertical axis represents distance between the moving structure and the transducer. The horizontal axis represents time. • Since only one scan line is imaged, M-mode echo provides greater sensitivity than 2-D echo for studying the motion of moving cardiac structures. • Motion and thickness of ventricular walls, changing size of cardiac chambers and opening and closure of valves is better displayed on M-mode (Fig. 2.2). Fig. 2.2: Motion-mode echo (M-mode Echo) levels: A. Mitral valve (MV) level B. Aortic valve (AV) level
  30. 30. Echo Made Easy18 Fig. 2.3: Continuous wave (CW) Doppler signal of stenotic aortic valve from multiple views; maximum velocity is 3 m/sec APX: apical 5 chamber view RPS: right parasternal view SSN: suprasternal notch • Simultaneous ECG recording facilitates accurate timing of cardiac events. Similarly, the flow pattern on color flow mapping can be timed in relation to the cardiac cycle. CONTINUOUS WAVE (CW) DOPPLER • CW Doppler transmits and receives ultrasound continuously. It can measure high velocities without any upper limit and is not hindered by the phenomenon of aliasing. • However, CW Doppler cannot precisely localize the returning signal which may originate anywhere along the length or width of the ultrasound beam (Fig. 2.3). • This Doppler modality is used for rapid scanning of the heart in search of high velocity signals and abnormal flow patterns. • Since the Doppler frequency shift is in the audible range, the audio signal is used to angulate and rotate the transducer in order to obtain the best visual display.
  31. 31. Conventional Echo 19 • CW Doppler display forms the basis for placement of “sample volume” to obtain PW Doppler spectral tracing. • CW Doppler is used for grading the severity of valvular stenosis and assessing the degree of valvular regurgitation. • An intracardiac left-to-right shunt such as a ventricular septal defect can be quantified. • By using CW Doppler signal of the tricuspid valve, pulmonary artery pressure can be calculated. PULSED WAVE (PW) DOPPLER • PW Doppler transmits ultrasound in pulses and waits to receive the returning ultrasound after each pulse. • Because of the time delay in receiving the reflected signal which limits the sampling rate, it cannot detect high velocities. • At velocities over 2 m/sec, there occurs a reversal of flow known as the phenomenon of aliasing. • However, PW Doppler provides a better spectral tracing than CW Doppler, which is used for calculations (Fig. 2.4). Fig. 2.4: Pulsed wave (PW) Doppler signal of a stenotic aortic valve from a single view; maximum velocity is 2 m/sec
  32. 32. Echo Made Easy20 • PW Doppler modality is used to localize velocity signals and abnormal flow patterns picked up by CW Doppler and color flow mapping, respectively. • The mitral valve inflow signal is used for the assessment of left ventricular diastolic dysfunction. • The aortic valve outflow signal is used for the calculation of stroke volume and cardiac output. CLINICAL APPLICATIONS OF ECHO 2-D Echo • Anatomy of heart and structural relationships. • Intracardiac masses and pericardial diseases. • Motion of ventricular walls and valvular leaflets. • Wall thickness, chamber volume, ejection fraction. • Calculation of stroke volume and cardiac output. • Architecture of valve leaflets and size of orifice. • Positioning for M-mode image and Doppler echo. M-Mode Echo • Cavity size, wall thickness and muscle mass. • Excursion of ventricular walls and valve cusps. • Timing of cardiac events with synchronous ECG. • Timing of flow pattern with color flow mapping. CW Doppler • Grading the severity of valvular stenosis. • Assessing degree of valvular regurgitation. • Quantifying the pulmonary artery pressure. • Scanning the heart for high velocity signal.
  33. 33. Conventional Echo 21 PW Doppler • Assessment of left ventricular diastolic function. • Calculation of stroke volume and cardiac output. • Estimation of orifice area of stenotic aortic valve. • Localization of flow pattern seen on CF mapping. • Localization of signal picked up on CW Doppler. • Application of spectral tracing for calculations.
  34. 34. 3 ColorColorColorColorColor DopDopDopDopDoppler Echopler Echopler Echopler Echopler Echo PRINCIPLES OF COLOR DOPPLER • Color Doppler echocardiography is an automated version of the pulsed-wave Doppler. It is also known as real-time Doppler imaging. • Color Doppler provides a visual display of blood flow within the heart, in the form of a color flow map. • The color flow map is rightly called a “non-invasive angio- gram” since it simultaneously displays both anatomical as well as functional information. • After a burst of ultrasound is reflected back along a single scan-line, as in pulsed-wave Doppler, it is analyzed by the autocorrelator of the echo-machine. • The autocorrelator compares the frequency of the returning signal with the original frequency. It automatically assigns a color-code to the frequency difference. • Analysis of several sample volumes down each scan-line and of several such scan-lines using multigate Doppler, creates a color-encoded map of the area being interrogated. • The color flow map encodes information about direction as well as velocity of blood flow. When this map is superimposed on the image sector of interest, appropriate interpretation is made.
  35. 35. Echo Made Easy24 • The colors assigned to blood flow towards the transducer are shades of red white colors assigned to flow away from the transducer are hues of blue (Fig. 3.1). • This is in accordance with the BART convention: Blue Away Red Towards • As the velocity of blood flow increases, the shade or hue assigned to the flow gets progressively brighter. Therefore, low velocities appear dull and dark while high velocities appear bright and light. • When blood flow at high velocity becomes turbulent, it superimposes color variance into the color flow map. This is seen as a mosaic pattern with shades of aquamarine, green and yellow (Fig. 3.2). • This reversal of color-code, as it “wraps around” and outlines the high velocity, is the color counterpart of aliasing observed on pulsed-wave Doppler. • The differences between a color flow map and a spectral trace obtained from pulsed-wave Doppler are summarized in Table 3.1. Fig. 3.1: Color flow map of a normal mitral valve from A4CH view showing a red-colored jet
  36. 36. Color Doppler Echo 25 Technique • The technique of color Doppler is similar to that of conventional echo and pulsed-wave Doppler. The transducer is placed in the usual parasternal or apical window as done for standard echo imaging. • Once an anatomical image is obtained, the color is turned on. Color flow maps are automatically displayed and superimposed on the standard echo image (Fig. 3.3). TABLE 3.1 Differences between spectral trace and color flow on Doppler Spectral trace Color flow Display Scan-line Flow-map Information Direction Color Velocity Value Shade Turbulence Aliasing Mosaic Fig. 3.2: Color flow map of a stenotic mitral valve from A4CH view showing a mosaic pattern
  37. 37. Echo Made Easy26 • When the color map has been visualized, the transducer is slightly angulated. This is done to optimize the visual display. The final image is often a trade-off between an optimal anatomical image and a good color flow map. • The gray-scale tissue-gain setting must be just enough to provide structural reference. Setting the tissue-gain too low blurs the anatomical image. Setting the tissue-gain too high induces gray-scale artefact or “background noise” and distorts the color display (Fig. 3.4). • The velocity-filter and color-gain settings must be optimal. Setting the filter high and gain low may miss color flow maps of low velocities. Setting the filter low and gain high may introduce color artefacts from normal structures and obscure genuine color flow maps. Advantages • The major advantage of color Doppler echo is the rapidity with which normal and abnormal flow patterns can be visualized and interpreted. • The spatial orientation of color flow mapping is easier to comprehend for those not experienced in Doppler. Fig. 3.3: Color flow map of ventricular outflow tract from A5CH view showing a blue jet
  38. 38. Color Doppler Echo 27 Conventional wave Doppler tracings have to be understood, before interpretation. • Color Doppler improves the accuracy of sampling with pulsed-wave and continuous-wave Doppler by helping to align the Doppler beam with the color jet. This facilitates localization of valve regurgitation and intracardiac shunts. • The phenomenon of aliasing, a disadvantage in pulsed-wave Doppler, is advantageous during color flow mapping. Introduction of color variance in the flow map is easily recognized as a mosaic pattern. Limitations • Like all other echo modalities, color Doppler may be limited by non-availability of a satisfactory echo window or by malalignment of the ultrasound beam with blood flow direction. • As with pulsed-wave Doppler, color Doppler is sensitive to pulsed repetition frequency (PRF) of the transducer and the depth of the cardiac structure being interrogated. • Color Doppler may inadvertently miss low velocities if the flow signal is weak. This occurs especially if the velocity filter setting is high and the color gain setting is low. Fig. 3.4: Color flow map of a regurgitant aortic valve from A5CH view showing a mosaic jet
  39. 39. Echo Made Easy28 • Color Doppler may spuriously pick up artefacts from heart muscle and valve tissue which falsely get assigned a color. This occurs especially if the velocity filter setting is low and the color gain setting is high (Fig. 3.5). • Complex cardiac lesions may produce a multitude of blood flows in a small area, in both systole and diastole. The result is a confusional riot of color, hindering rather than helping an accurate diagnosis. APPLICATIONS OF COLOR DOPPLER Stenotic Lesions • Color Doppler can identify, localize and quantitate stenotic lesions of the cardiac valves. It visually displays the stenotic area and the resultant jet as distinct from normal flow. • Stenosis of a valve produces a “candle-flame” shaped jet at the site of narrowing. The jet color assumes a mosaic pattern of aquamarine, green and yellow signifying increased velocity and turbulent flow (Fig. 3.6). • The color Doppler signal has to be parallel to the direc- tion of blood flow or else the degree of stenosis gets Fig. 3.5: Color flow map of the left ventricle from A5CH view showing artefacts from the IV septum and mitral leaflets
  40. 40. Color Doppler Echo 29 underestimated. Angulation of the transducer to improve the Doppler signal, inadvertently skews and distorts the anatomical image. • When there is calcification of the valve leaflets or annulus, the color flow display drops out of the image in the calcified area. Turning up the gain to image the calcified area causes blooming of both the anatomic image as well as the Doppler signal. • It would be ideal to measure the stenotic orifice from the color Doppler view. However, this is practically difficult since anatomical measurement requires perpendicular beam orientation while the Doppler signal requires a parallel beam orientation. Regurgitant Lesions • Color Doppler can diagnose and estimate the severity of regurgitant lesions of the valves. It displays the regurgitant jet as a flow-map distinct from the normal flow pattern. • A regurgitant valve produces a color flow map in the receiving chamber. For instance, mitral regurgitation results in a left atrial flow map while aortic regurgitation causes a flow map in the left ventricular outflow tract (Fig. 3.7). Fig. 3.6: Color flow map of stenotic aortic valve from A5CH view showing change in color to a mosaic pattern
  41. 41. Echo Made Easy30 • A jet interrogated along its length produces a large flow area while scanning the same jet across reveals a smaller area. By using multiple views and windows for interrogation, the size and geometry of a pathological jet can be accurately estimated. • It is necessary to angulate the transducer, in order to scan across the length and width of the chamber being studied. This will improve the detection of eccentric regurgitant lesions. • Valvular regurgitation can be quantified by assessing the depth upto which color flow can be picked up. Mild regur- gitation is confined to the valve plane while severe regurgitation can be mapped upto the distal portion of the receiving chamber. • Measuring the absolute jet area and calculating the ratio of jet area to atrial size is also used to assess the degree of ventriculoatrial regurgitation. • A ratio of less than 25% indicates mild, 25 to 50% suggests moderate and more than 50% represents severe valvular regurgitation. Fig. 3.7: Color flow map of a regurgitant mitral valve from PLAX view showing a jet in the left atrium
  42. 42. Color Doppler Echo 31 Intracardiac Shunts • An atrial septal defect produces a mosaic color flow map crossing from the left atrium to the right atrium. Because of low velocity, the color map is sometimes missed (Fig. 3.8). • A ventricular septal defect produces a mosaic color flow map extending from the left ventricle to the right ventricle across the septum. The width of the map approximates the size of the septal defect. • A patent ductus arteriosus produces a retrograde mosaic color flow map extending from the descending aorta to the pulmonary artery. Fig. 3.8: Color flow map of an atrial septal defect from PSAX view showing a jet from the left atrium to right atrium
  43. 43. 4 The EchoThe EchoThe EchoThe EchoThe Echo WWWWWindowsindowsindowsindowsindows TRANSTHORACIC ECHO • Conventional echocardiography is performed from the anterior chest wall (precordium) and is known as transthoracic echo. • Echocardiography can also be performed from the eso- phagus which is known as transesophageal echo. • For transthoracic echo, the subject is asked to lie in the semirecumbent position on his or her left side with the head slightly elevated. • The left arm is tucked under the head and the right arm lies along the right side of the body. • This position opens the intercostal spaces through which echocardiography can be performed, while most of the heart is masked from the ultrasound beam by the ribs. • Better images are obtained during expiration when there is least ‘air-tissue’ interface. • Ultrasound is transmitted from a transducer having a frequency of 2.5 to 3.5 MHz for echo in adults. • This frequency is used to study deep seated structures because of better penetration.
  44. 44. Echo Made Easy34 • A transducer frequency of 5.0 MHz is suitable for pediatric echo, since the heart is more superficial in children. • Ultrasound jelly is applied on the transducer and it is placed on the chest at the site of an “echo window”. • Most of the time, the left parasternal and apical windows are routinely used. • The transducer has a reference line or dot on one side, in order to orient it in the correct direction, for obtaining various echo views. • The transducer is variably positioned, in terms of location and direction, for different echo images. • It can be tilted (superiorly or inferiorly), to bring into focus the structure of interest and rotated (clockwise or anticlockwise), to fine-tune the image. STANDARD ECHO WINDOWS • Standard locations on the anterior chest wall are used to place the transducer, which are called “echo windows” (Fig. 4.1). These are: – left parasternal – apical Fig. 4.1: The standard “windows” used during echocardiography
  45. 45. The Echo Windows 35 – subcostal – right parasternal – suprasternal. • Standard windows are important for two reasons: – penetration of ultrasound waves from windows is good, without much masking of image or absorption of ultrasound by ribs and lungs. – standardized echo images can be compared with studies performed by different observers or on different occasions by the same observer. • Transthoracic echo may be technically difficult to perform in the following situations: – severe morbid obesity – chest wall deformity – pulmonary emphysema. Parasternal Long-Axis View (PLAX View) (Fig. 4.2) • Transducer position: left sternal edge; 2nd–4th space • Marker dot direction: points towards right shoulder. Fig. 4.2: The parasternal long-axis (PLAX) view
  46. 46. Echo Made Easy36 Structures seen: – proximal aorta – aortic valve – left atrium – mitral valve – left ventricle – IV septum – posterior wall – right ventricle – pericardium. • Most echo studies begin with this view. It sets the stage for subsequent echo views. Parasternal Short-Axis Views (PSAX Views) (Fig. 4.3) • Transducer position: left sternal edge; 2nd–4th space • Marker dot direction: points towards left shoulder (90° clockwise from PLAX). • By tilting the transducer on an axis between the left hip and right shoulder, short-axis cuts are obtained at different levels, from the aorta to the LV apex (Fig. 4.3). • This angulation of the transducer from the base to apex of the heart for short-axis views is known as “bread-loafing”. Short Axis Levels (Fig. 4.3) 1. pulmonary artery 2. aortic valve level 3. mitral valve level 4. papillary muscle 5. left ventricle.
  47. 47. The Echo Windows 37 Pulmonary Artery (PA) Level (Fig. 4.4) Structures seen: – pulmonary artery – pulmonary valve – RV outflow tract. Fig. 4.3: The parasternal short-axis (PSAX) views
  48. 48. Echo Made Easy38 Aortic Valve (AV) Level (Fig. 4.5) Structures seen: – aortic valve cusps – left atrium Fig. 4.4: PSAX view: pulmonary artery (PA) level Fig. 4.5: PSAX view: aortic valve (AV) level
  49. 49. The Echo Windows 39 – interatrial septum – tricuspid valve – RV outflow tract. Mitral Valve (MV) Level (Fig. 4.6) Structures seen: – mitral valve orifice – mitral valve leaflets – ventricular septum Papillary Muscle (PM) Level (Fig. 4.7) Structures seen: – anterolateral PM (3o) – posteromedial PM (7o ) – anterior wall (12o to 3o) – lateral wall (3o to 6o) – inferior wall (6o to 9o ) – IV septum (9o to 12o) • For apical views, the subject turns back rightwards from the left lateral position and lies more supine. Fig. 4.6: PSAX view: mitral valve (MV) level
  50. 50. Echo Made Easy40 Apical 4-Chamber View (A4CH View) (Fig. 4.8) • Transducer position: apex of the heart • Marker dot direction: points towards left shoulder. Structures seen: – right and left ventricle – right and left atrium – mitral, tricuspid valves Fig. 4.7: PSAX view: papillary muscle (PM) level Fig. 4.8: Apical 4-chamber (A4CH) view
  51. 51. The Echo Windows 41 – IA and IV septum – left ventricular apex – lateral wall left ventricle – free wall right ventricle. Apical 5-Chamber View (A5CH view) (Fig. 4.9) • The A5CH view is obtained after the A4CH view by slight downward tilting of the transducer. The 5th chamber added is the left ventricular outflow tract (LVOT). • Transducer position: as in A4CH view. • Marker dot direction: as in A4CH view. Structures seen: As in A4CH view. Additionally: — LV outflow tract — aortic valve — proximal aorta. Fig. 4.9: Apical 5-chamber (A5CH) view
  52. 52. Echo Made Easy42 Subcostal View • For subcostal view, the position of the subject is different from that used to obtain parasternal and apical views. • The subject lies supine with the head held slightly low, feet planted on the couch and the knees slightly flexed. • Better images are obtained with the abdomen relaxed and during the phase of inspiration. • Transducer position: under the xiphisternum • Marker dot position: points towards left shoulder. Structures seen: As in A4CH view. • The subcostal view is particularly useful when transthoracic echo is technically difficult because of the following reasons: – severe morbid obesity – chest wall deformity – pulmonary emphysema. • The following structures are better seen from the subcostal view than from the apical 4-chamber view: – inferior vena cava – descending aorta – interatrial septum – pericardial effusion. Suprasternal View • For suprasternal view, the subject lies supine with the neck hyperextended by placing a pillow under the shoulders. The head is rotated slightly towards the left. • The position of arms or legs and the phase of respiration have no bearing on this echo window. • Transducer position: suprasternal notch. • Marker dot direction: points towards left jaw.
  53. 53. The Echo Windows 43 Structures seen: – ascending aorta – pulmonary artery. Right Parasternal View • For right parasternal view, the subject lies in the semi- recumbent position on the right side. The right arm is tucked under the head and the left arm lies along the left side of the body. • In other words, this position is the mirror-image of that used for the left parasternal view. • Transducer position: right sternal edge; 2nd–4th space • Marker dot direction: points towards left shoulder. Structures seen: – aortic valve – aortic root. TRANSESOPHAGEAL ECHO Principle • During echocardiography, a balance has to be struck between tissue penetration and image resolution. Low frequency transducers have good penetration (less attenuation) but relatively poor resolution. On the other hand, high frequency transducers have poor penetration (more attenuation) but better resolution. • Anatomically speaking, the esophagus in its mid-course is strategically located posterior to the heart and anterior to the descending aorta. This provides an opportunity to interrogate the heart and related mediastinal structures with a high frequency transducer positioned in the esophagus for better image resolution. • The technique is known as transesophageal echocardio- graphy or simply TEE.
  54. 54. Echo Made Easy44 Technique • A miniature transducer is mounted onto a probe or gastroscope similar to the one employed for upper gastrointestinal endoscopy. The scope is advanced to various depths in the esophagus to examine cardiac and related structures. By manoeuvring the transducer and the angle of beam from controls on the handle, different views of the heart are obtained. • This ‘back-door’ approach to echocardiography has both advantages and disadvantages. Advantages • Useful alternative to transthoracic echo if the latter is technically difficult due to obesity, chest wall deformity, emphysema or pulmonary fibrosis. • Useful complement to transthoracic echo because of better image quality and resolution due to two reasons: – absence of acoustic barrier between the ultrasound beam and the rib cage, chest wall and lung tissue. – greater proximity to the heart and therefore the ability to use higher frequency probe with vastly improved image quality and precise spatial resolution. • Useful supplement to transthoracic echo, which cannot examine the posterior aspect of the heart. Structures such as left atrial appendage, descending aorta and pulmonary veins can only be visualized by TEE. Disadvantages • It is a semi-invasive procedure which is uncomfortable to the patient, more time consuming and carries a small risk of serious complications such as oropharyngeal or esophageal trauma, cardiac arrhythmias and laryngo-bronchospasm (Table 4.1).
  55. 55. The Echo Windows 45 • It requires short-term sedation, oxygen administration and ECG monitoring since, there are chances of hypoxia, arrhythmia and angina. Rarely, respiratory depression or allergic reactions may occur. • TEE is contraindicated in the presence of active bleeding or coagulopathy, esophageal abnormalities, unstable cervical arthritis and poor cardiopulmonary status (Table 4.2). • The transesophageal echo (TEE) views are significantly different from standard transthoracic echo views. Novel TEE images require a comprehensive understanding of the spatial relationship between cardiac structures. It would be beyond the scope and against the philosophy of this book to understand and learn these views in detail. Nevertheless, the indications for TEE are duly mentioned at appropriate places, in several chapters of the book. TABLE 4.1 Complications with TEE Major • Esophageal rupture or perforation • Laryngospasm or bronchopasm • Sustained ventricular tachycardia Minor • Retching and vomiting • Sore-throat and hoarseness • Blood-tinged sputum • Tachycardia or bradycardia • Hypoxia and ischemia • Transient BP rise or fall
  56. 56. Echo Made Easy46 FUTURE DIRECTIONS IN ECHO Three-Dimensional Echo • Two-dimensional echocardiography (2-D echo) provides a 2-D view of the 3-D heart. Therefore, a series of integrated 2-D views are required to mentally construct a three- dimensional (3-D) image of the structure of the heart. • To accurately perform this task, knowledge of the precise relationship of each 2-D image with the other is vital but not always feasible. • For instance, while quantifying cardiac chamber volume and function with 2-D echo, one makes certain assumptions about cardiac geometry to apply specific formulae for calculations. • As chambers get distorted in shape by infarction and remodeling, these geometric assumptions lose their accuracy as do the calculated values from formulae. • Three-dimensional echocardiography (3-D echo) obviates the need for cognitive 3-D reconstruction of 2-D image planes TABLE 4.2 Contraindications to TEE Absolute • Uncooperative patient • Poor cardiorespiratory status • Esophageal obstruction • Tracheoesophageal fistula • Active bleed or coagulopathy Relative • Large esophageal varices • Prior esophageal surgery • Unstable cervical arthritis • Atlantoaxial dislocation
  57. 57. The Echo Windows 47 and the compulsion of making geometric assumption about the shape of cardiac structures for quantification. • Besides its application in ventricular volumetric assessment, 3-D echo is particularly useful to study asymmetrical stenotic valve orifices, eccentric regurgitant jets picked up by color Doppler and complex structural relationships observed in congenital heart diseases. • The 3-D echo can be viewed from various projections by rotation of the images, to enhance the appreciation of structural relationships. • Three-dimensional echocardiography (3-D echo) has the potential to reduce the time required for complete cardiac image acquisition. • As computer hardware and software matures and transdu- cer technology evolves, time and labor-intensive offline image reconstruction will soon be replaced by real-time image acquisition. • Three-D echo therefore has the potential to move from being merely a research tool to being used extensively in the clinical arena. Myocardial Contrast Echo • Myocardial contrast echocardiography involves the appli- cation of an ultrasonic contrast agent, to accurately delineate areas of reduced myocardial blood flow or perfusion defects related to coronary occlusion. • The contrast agent exists as microbubbles which are produced either by electromechanical sonication or by lipid encapsulation. • Myocardial contrast imaging has the ability to enhance qualitative as well as quantitative information pertaining to myocardial perfusion.
  58. 58. Echo Made Easy48 • In the emergency setting, contrast imaging provides incre- mental prognostic information in patients who have resting abnormalities in regional wall motion. • Patients of acute coronary syndrome with both abnormal wall motion and abnormal perfusion have worse event-free survival when compared to patients with normal myocardial perfusion. • In the acute setting, contrast imaging can identify patients with the “no-reflow” phenomenon which is characterized by lack of recovery in microvascular perfusion despite success- ful opening of the occluded coronary artery by intervention or thrombolysis. • The long-term prognosis of these “no-reflow” patients is adverse and they are observed to have significant deterio- ration in regional and global systolic function at follow-up. • In the chronic setting, contrast imaging can also identify viability of the perfusion bed subtended by the occluded coronary artery, when contrast injection into an adjacent coronary artery produces enhancement. • This is clinical relevant because revascularization after myocardial infarction results in improved function only when viable myocardium is demonstrable. • Finally, during exercise or dobutamine stress echocardio- graphy, real-time assessment of myocardial perfusion imp- roves the sensitivity of the test in detecting angiographically significant stenosis, compared to wall motion analysis alone. Tissue Doppler Imaging • During day-to-day echocardiography, left ventricular function is routinely evaluated by two-dimensional (2-D) and motion- mode (M-mode) techniques. • However, visual evaluation of LV function using these modalities suffers from the limitations of being significantly subjective and provides only semi-quantitative data.
  59. 59. The Echo Windows 49 • Moreover, visual assessment has limited ability to detect subtle changes in LV function and in timing of wall motion, throughout entire systole and diastole. • Tissue Doppler imaging is a more objective and highly quantitative method to accurately assess regional and global left ventricular systolic and diastolic function. • This technique can measure a variety of myocardial func- tional parameters which include tissue velocity, acceleration, displacement and strain rate. • Tissue Doppler imaging has been used as a diagnostic tool in specific situations including assessment of myocardial ischemia, evaluation of diastolic dysfunction and differen- tiation between restrictive cardiomyopathy and constrictive pericarditis. • Myocardial ischemia is diagnosed by velocity imaging as reduced systolic ejection velocity and higher postsystolic shortening velocity. Findings on strain imaging are reduced systolic shortening along with systolic lengthening. • Heart failure with preserved ejection fraction (HFPEF) accounts for a significant chunk of heart failure patients particularly in the elderly population. • These patients have isolated or predominant diastolic heart failure allowing for the fact that ejection fraction (EF) may fail to identify mild systolic dysfunction. • Additionally, there are patients who do not have heart failure but have impaired diastolic function such as patients with systemic hypertension and diabetes mellitus. • The characteristic findings in diastolic dysfunction observed by tissue Doppler imaging is reduced early diastolic mitral annulus velocity, which correlates with peak LV lengthening velocity.
  60. 60. Echo Made Easy50 • This abnormality is observed across the entire range of diastolic dysfunction from impaired relaxation (reduced E/A ratio) through pseudo-normal filling (normal E/A ratio) to restrictive filling (increased E/A ratio). • Patients with constrictive pericarditis have normal systolic function and ventricular relaxation while those with restrictive cardiomyopathy have impairment of both parameters. • Therefore, reduced early diastolic mitral annulus velocity is more indicative of restrictive cardiomyopathy whereas there is substantial overlap in transmitral filling velocities between these patients, those with constrictive pericarditis and even normal subjects.
  61. 61. 5 NorNorNorNorNormal Vmal Vmal Vmal Vmal Viewsiewsiewsiewsiews and Vand Vand Vand Vand Valuesaluesaluesaluesalues ECHO INTERPRETATION • The echocardiogram provides a substantial amount of structural and functional information about the heart. While still frames provide anatomical detail, dynamic images tell us about physiological function. • Echocardiography is quite easy to understand, since many echo features are based upon simple physical facts and physiological principles. • Nevertheless, the value of information derived from echo depends heavily upon who has performed the study. The quality of an echo is highly operator dependent and proportional to his experience and skill. • The abnormal can only be viewed in the light of the normal. Therefore, it is important to appreciate normal echo images and to be familiar with normal dimensions. SCANNING SEQUENCE A suggested schematic for a systematic and detailed echocardiography study is as follows: • Start with the parasternal long-axis view.
  62. 62. Echo Made Easy52 • Make M-mode recording at these 3 levels: – level of aortic valve – level of mitral valve – level of left ventricle. • Rotate the transducer by 90° clockwise. Angulate it from the base to apex to obtain short-axis views at these 4 levels: – pulmonary artery level – aortic valve level – mitral valve level – papillary muscle level. • Go on to the apical 4-chamber view. Measure ventricular volumes in systole and diastole (to assess LV systolic function). • Turn on the color flow mapping for abnormal flow patterns due to valvular diseases or septal defects. • Place the pulsed wave (PW) Doppler ‘sample volume’ in the LV cavity at the tips of MV leaflets in the diastolic position (to assess LV diastolic function). • Angulate the transducer anteriorly to obtain the apical 5-chamber view. Place the ‘sample volume’ in the aortic valve to obtain the flow velocity integral (FVI). Calculate the stroke volume and from it the cardiac output. • Use continuous wave (CW) Doppler to scan the apical 4-chamber view for high velocity signal, if abnormal flow is observed on color flow mapping. • Use pulsed wave (PW) Doppler to localize an abnormal flow seen on color flow mapping or a high velocity signal picked on CW Doppler. • Use other echo windows (subcostal, suprasternal and right parasternal) as and when indicated. • Rotate the transducer by 45° anticlockwise and obtain the apical 2-chamber view.
  63. 63. Normal Views and Values 53 WHAT IS NORMAL? It must be borne in mind that normal value ranges of echo-derived dimensions, depend upon several factors. These factors include height, sex, age and the level of physical activity. Normal values are higher in these subjects: – male gender – tall persons – trained athletes – elderly patients. Therefore, correction for these factors is made by indexing cardiac dimensions to body surface area (BSA) using the formula: 2 height(cm) × weight(kg) BSA(m ) = 3600 Normal dimensions are estimated from small populations of ‘average’ persons and may not apply to unusually small or tall subjects, to the elderly or to athletes. NORMAL VARIANTS Some findings on echo may be normal and must be carefully understood to avoid overdiagnosis of heart disease (Fig. 5.1). Normal Structures • Moderator band in the apical one-third of the right ventricle, parallel to the plane of the tricuspid valve. • False tendon in the left ventricle, extending between the lateral papillary muscle and the IV septum. • Eustachian valve in the right atrium, guarding the opening of the inferior vena cava. • Reverberation artefact in the left atrium, from calcific mitral annulus or prosthetic aortic valve.
  64. 64. Echo Made Easy54 Normal Flow Patterns • Trivial tricuspid regurgitation is observed in many subjects. • Minimal mitral regurgitation is observed in some subjects • Aortic regurgitation is observed only from diseased valves. Normal Findings in Elderly • Mild thickening of aortic valve leaflets (misdiagnosed as aortic valve stenosis). • Mitral annular ring calcification with regurgitation (misdiagnosed as vegetation or thrombus). • Reduced LV compliance, A/E ratio > 1 on Doppler (misdiagnosed as LV diastolic dysfunction). • Localized subaortic bulge of ventricular septum (misdiagnosed as septal hypertrophy or HOCM). Fig. 5.1: Normal structural variants seen on echo: A. Moderator band in right ventricle B. False tendon in the left ventricle C. Mitral annular ring calcification D. Subaortic bulge of IV septum
  65. 65. Normal Views and Values 55 NORMAL DIMENSIONS • Most echo studies begin with the parasternal long-axis (PLAX) view. It sets the stage for subsequent echo views. • Traditionally, dimensions are measured using M-mode scan which has better resolution than 2-D echo. • However, despite this theoretical advantage, M-mode imaging may be inaccurate unless the cursor is placed perpendicular to the structure being measured. Practically speaking, this is not always possible. • In that case, measurements can instead be made from the 2-D image of PLAX view (Fig. 5.2). • An experienced echocardiographer can often give a reasonably good visual assessment of LV systolic function from the PLAX view without actual measurements. • However, this rough assessment may be unreliable for serial evaluation of LV function and when LV volumes critically influence the timing of a surgical intervention. • The PLAX view gives a good visual impression of the motion of the interventricular septum (IVS) and the left ventricular posterior wall (LVPW) (Fig. 5.3). Fig. 5.2: Measurement of dimensions from PLAX view
  66. 66. Echo Made Easy56 Parasternal Long-Axis View (PLAX View) The PLAX view is used to measure the dimensions of the aortic annulus, sinus of Valsalva, aortic root and the anterior aortic swing (Fig. 5.4). Aortic annulus 17–25 mm Sinus of Valsalva 22–36 mm Sinotubular junction 18–26 mm Fig. 5.3: Motion of IVS and LVPW seen on PLAX view Fig. 5.4: Dimensions of proximal aorta from PLAX view
  67. 67. Normal Views and Values 57 Aortic root (tubular) 20–37 mm Anterior aortic swing 7–15 mm Aortic valve orifice area 2.5–3.5 cm2 M-Mode Scan PLAX View Aortic Valve Level (Fig. 5.5) Aortic root diameter 20–37 mm Aortic cusp separation 15–26 mm Left atrial diameter 19–40 mm Mitral Valve Level (Fig. 5.6) AML D-E excursion 20–35 mm AML E-F slope 18–120 mm/sec E point to septum less than 5 mm Note – The diameter of the aortic root is measured between the leading edges of the anterior and posterior aortic walls. – The diameter of the left atrium is measured between the leading edges of the anterior and posterior atrial walls. Fig. 5.5: M-mode scan PLAX view; aortic valve level
  68. 68. Echo Made Easy58 Ventricular Level (Fig. 5.7) IV-septal thickness (diastolic) 6–12 mm Posterior wall thickness (diastolic) 6–11 mm IV-septal excursion (systolic) 6–9 mm Posterior wall excursion (systolic) 9–14 mm LV diameter end-diastolic (LVEDD) 36–52 mm LV diameter end-systolic (LVESD) 24–42 mm RV internal dimension 7–23 mm RV free-wall thickness < 5 mm LV fractional shortening 30–45% LV ejection fraction 50–75% Fig. 5.6: M-mode scan PLAX view; mitral valve level Fig. 5.7: M-mode scan PLAX view; ventricular level
  69. 69. Normal Views and Values 59 Note – The dimensions of the left ventricle are measured just below the free edge of the anterior mitral leaflet. – This standard level is important in order to compare serial studies performed on different occasions. Parasternal Short-Axis View (PSAX View) Pulmonary Artery Level Pulmonary artery diameter 18–15 mm Pulmonary outflow velocity 0.5–1.0 m/sec (mean 0.75 m/sec) Aortic Valve Level Aortic root dimension 20–37 mm Left atrial diameter 19–40 mm Mitral Valve Level Mitral valve orifice 4–6 cm2 Apical 4-Chamber View (A4CH View) LV volume end-diastolic 85 + 15 ml/m2 LV volume end-systolic 35 + 5 ml/m2 Mitral inflow velocity 0.6–1.4 m/sec (mean 0.9 m/sec) Tricuspid inflow velocity 0.3–0.7 m/sec (mean 0.5 m/sec)
  70. 70. Echo Made Easy60 Apical 5-Chamber View (A5CH View) Aortic outflow velocity 0.9–1.8 m/sec (mean 1.3 m/sec) Stroke volume 32–48 ml/beat/m2 Cardiac output 2.4–4.2 L/min/m2 NORMAL VALVES Mitral Valve • The mitral valve consists of 2 leaflets: – anterior mitral leaflet (AML). – posterior mitral leaflet (PML). • Motion of both the leaflets is visualized by M-mode scanning from the PLAX view. • The excursion of the AML can be divided into the following waves and slopes (Fig. 5.8): E-wave : Anterior and posterior motion during entire diastole. D-E slope : Anterior motion during rapid diastolic filling. Fig. 5.8: M-mode tracing of the mitral valve
  71. 71. Normal Views and Values 61 E-F slope : Posterior motion during end-diastolic relaxation. A-wave : Anterior motion during atrial systolic contraction • The amplitude of motion of the PML is less than that of the AML and in an opposite direction. Tricuspid Valve • The tricuspid valve consists of 3 leaflets: – large anterior leaflet (ATL), – small septal leaflet (STL) – tiny posterior leaflet (PTL). • The ATL motion is visualized by M-mode scanning from the PLAX view in the right ventricle, anterior to the IV septum. • The excursion of the ATL is very similar to that of the AML of mitral valve described above (Fig. 5.9). • The STL is only recorded when there is dilatation of the right ventricle or clockwise rotation due to emphysema. Fig. 5.9: M-mode tracing of the tricuspid valve
  72. 72. Echo Made Easy62 • The amplitude of motion of the STL is less than that of the ATL and in a direction opposite to ATL excursion. • The PTL is not visualized on M-mode tracing. Aortic Valve • The aortic valve consists of 3 cusps: – anterior right coronary cusp (RCC) – posterior non-coronary cusp (NCC) – middle left coronary cusp (LCC). • The RCC and NCC are visualized by M-mode scanning from the PLAX view (Fig. 5.10). • During systole, the anterior and posterior cusps move away from each other and towards the anterior and posterior aortic walls respectively. • This creates a box-like systolic opening of the valve, in the shape of a parallelogram. • During diastole, the cusps oppose to form a central closure line in the aortic lumen. The closure line is equidistant from the anterior and posterior aortic walls. Fig. 5.10: M-mode tracing of the aortic valve
  73. 73. Normal Views and Values 63 Pulmonary Valve • The pulmonary valve consists of 3 cusps: – posterior (left) cusp – anterior cusp – right cusp. The only cusp usually recorded by M-mode scanning from the PLAX view is the posterior (left) cusp (Fig. 5.11). • The anterior and right cusps are infrequently visualized due to obliquity of the valve to the ultrasound beam. • The excursion of the posterior pulmonary leaflet can be divided into the following slopes (Fig. 5.11): – B-C slope : systolic opening motion – C-D slope : open valve during systole – D-E slope : systolic closing motion – E-F slope : diastolic posterior motion. Fig. 5.11: M-mode tracing of the pulmonary valve
  74. 74. 6 VVVVVentricularentricularentricularentricularentricular DysfunctionDysfunctionDysfunctionDysfunctionDysfunction Assessment of ventricular function, particularly of the left ventricle, is the most common and the most important application of echocardiography. Presence of left ventricular dysfunction is a reliable prognostic indicator in all forms of cardiac disease. It has important therapeutic implications and many a time, clinical management is altered when an abnor- mality of ventricular function is detected. Ventricular dysfunction can be classified as: – Left ventricular systolic dysfunction – Left ventricular diastolic dysfunction – Right ventricular dysfunction. LV SYSTOLIC DYSFUNCTION In order to understand LV systolic dysfunction, it is important to know the normal indices of left ventricular function. Normal Indices LV wall thickness in diastole 6–12 mm interventricular septum (IVS) 6–11 mm LV posterior wall (LVPW)
  75. 75. Echo Made Easy66 LV wall excursion in systole 3–8 mm interventricular septum (IVS) 9–14 mm LV posterior wall (LVPW) LV internal dimension 24–42 mm at end-systole (LVESD) 36–52 mm at end-diastole (LVEDD) LV internal volume 35 ± 5 ml at end-systole (LVESV) 85 ± 15 ml at end-diastole (LVEDV) Fractional shortening 30–45% (% change in LV dimension) LV ejection fraction 50–75% (% change in LV volume) Echo Features of LV Systolic Dysfunction M-Mode LV Level • During ventricular systole, the interventricular septum (IVS) and the left ventricular posterior wall (LVPW) move towards each other. • The amplitude of this motion is reduced in the presence of LV systolic dysfunction (Fig. 6.1). • LV internal dimension in end-systole (LVESD) and end- diastole (LVEDD) are measured on the M-mode tracing in the parasternal long-axis view (PLAX), at the level of mitral valve (MV) leaflet tips. • Measurements are taken from the endocardial lining of the septum (IVS) to that of the posterior wall (LVPW). • LV dimensions are increased in the presence of left ventricular systolic dysfunction.
  76. 76. Ventricular Dysfunction 67 • The percentage change in LV internal dimension between systole and diastole is called fractional shortening (FS). LVEDD – LVESD FS = ____________________ × 100% LVEDD The normal range of fractional shortening is 30–45%. • Reduced fractional shortening is an indicator of systolic dysfunction of the left ventricle. • However, in the presence of regional wall motion abnormality, fractional shortening does not reliably reflect the overall LV systolic performance. • The normal volume of the left ventricle during end-diastole (LVEDV) is 85±15 ml. • A volume greater than 100 ml is indicative of LV systolic dysfunction due to myocardial disease (cardiomyopathy or myocardial infarction) or because of volume overload (mitral or aortic regurgitation). Fig. 6.1: M-mode scan of the left ventricle showing: A. Reduced excursion of IVS and LVPW B. Increased dimension of the LV cavity
  77. 77. Echo Made Easy68 • The LV volume is derived from the ‘Cubed equation’ V = D3 V: volume; D: diameter • This equation is based on the assumption that the LV cavity is ellipsoid in shape and the major axis is twice the minor axis (Fig. 6.2). But this is not always true. • The LV volume derived from the Teicholz equation gives a more realistic and accurate measurement 7 V = ____________ × D3 2.4 + D • Measurement of LV dimensions can be unreliable if septal motion is abnormal due to old infarction, left bundle branch block or RV volume overload. • The percentage change in LV volume between systole and diastole is called ejection fraction (EF): LVEDV – LVESV EF = ___________________ × 100% LVEDV The normal range of ejection fraction is 50 to 75%. Fig. 6.2: Simulation of left ventricle cavity as an ellipsoid. Major axis (L) is twice the minor axis (D). LV volume = D3 by the cubed equation.
  78. 78. Ventricular Dysfunction 69 • Reduced ejection fraction is an indicator of LV systolic dysfunction. However, the ejection fraction also depends upon ventricular loading (preload and afterload). • The normal diastolic thickness of the left ventricular walls, that is interventricular septum (IVS) and left ventricular posterior wall (LVPW), is 6 to 12 mm. • Walls thinner than 6 mm indicate to stretching due to cardiomyopathy or scarring due to myocardial infarction. • Walls thicker than 12 mm indicate the presence of left ventricular hypertrophy. • Normally, the walls should thicken in systole. Reduced systolic thickening of walls indicates presence of LV systolic dysfunction, either global (cardiomyopathy) or regional (myocardial infarction). 2-D Echo A4CH View • 2-D echo can also be used to estimate LV volume in end-diastole (LVEDV) and end-systole (LVESV). • This is done by tracing the LV endocardial borders of a systolic and a diastolic LV frame while the software of the echo machine calculates the LV volumes. • From these volumes, the ejection fraction (EF) is calculated: LVEDV – LVESV EF = ____________________ × 100% LVEDV • The above method of calculating LV volume relies on manual tracing of the ventricular endocardial outline. Alternatively, LV volume can be calculated totally by the computer using the Simpson’s method.
  79. 79. Echo Made Easy70 • By this method, the left ventricle is divided into 20 sections of equal thickness. The computer takes multiple short-axis slices at different levels (Fig. 6.3). The volume of each slice is the area multiplied by its thickness. The sum of volumes of all slices is the volume of the left ventricle. Area of each slice = π (D/2)2 D is diameter Thickness of slice = 1/20 × LV LV is length Volume of each slice = Area × Thickness Left ventricle volume = Sum of all volumes • The cardiac output can also be obtained using LV volumes by the following simple calculations: Stroke volume (SV) = LVEDV – LVESV Cardiac output (CO) = SV × Heart rate (HR) Fig. 6.3: Estimation of the left ventricular volume by Simpson’s method; D is LV diameter
  80. 80. Ventricular Dysfunction 71 Doppler Echo • The cardiac output as an indicator of LV systolic function can be calculated from the peak aortic flow velocity (Vmax). This is obtained by Doppler display of aortic outflow from the apical 5 chamber (A5CH) view (Fig. 6.4). • Continuous wave (CW) Doppler is used to measure higher velocities and pulse wave (PW) Doppler for lower velocities. PW Doppler provides a better spectral tracing. • Before going into calculations of cardiac output, one must know the normal indices of ventricular ejection: Stroke volume = 32–48 ml/beat/m2 Cardiac output = 2.8–4.2 L/min/m2 Fig. 6.4: Calculation of the cardiac output from peak aortic flow velocity (Vmax) FVI = flow velocity integral AT = acceleration time PEP = pre-ejection period DT = deceleration time LVET = LV ejection time
  81. 81. Echo Made Easy72 Doppler Calculations Cardiac output = SV × HR SV : stroke volume HR : heart rate Stroke volume = CSA × FVI CSA: cross-sectional area FVI : flow velocity integral        2 2 2 222 D CSA r (D / 2) 0.785D 7 4 D : aortic annulus diameter (Fig. 6.5) • The FVI is calculated by the computer software of most echo machines as the area under curve of aortic outflow velocity spectral display. CO = 0.785 D2 × FVI × HR • Using similar calculations, the stroke volume of the right side of heart can be obtained using the peak pulmonary flow velocity (Vmax) and diameter of the pulmonary valve. Fig. 6.5: Measurement of aortic annulus diameter (D) to calculate aortic valve area
  82. 82. Ventricular Dysfunction 73 • Thereafter, the ratio of pulmonary flow (Qp) to systemic flow (Qs) which is the Qp: Qs ratio, can be calculated to quantify a cardiac shunt (see Congenital Diseases). Pitfalls in the Diagnosis of LV Systolic Dysfunction • LV internal dimensions are taken between endocardial surfaces of IVS and LVPW. Errors in measurement may occur if a prominent papillary muscle or a calcified mitral annulus is mistaken for the endocardial surface of LVPW. • As a differentiating feature, only the LVPW thickens in systole. Abnormal septal motion (e.g. LBBB) makes fractional shortening difficult to measure. • The normal range for LVEDD and LVESD varies with a number of factors including age, sex, height and body habitus. This should always be borne in mind. • Measurement of LV dimensions can be unreliable in the presence of abnormal wall motion due to infarction and abnormal septal motion due to left bundle branch block or RV volume overload. • Reduced LV systolic function is usually but not always associated with increased LV dimensions. • For instance, a large akinetic segment of the LV wall following myocardial infarction may impair LV systolic function but LV dimensions may be within the normal range. • An experienced echocardiographer can often give a reasonably good visual assessment of LV systolic function from the PLAX view, without actual measurements. • However, this rough assessment may be unreliable for serial evaluation of LV function and when LV volumes critically influence the timing of a surgical intervention.
  83. 83. Echo Made Easy74 • There may be interobserver and even more surprisingly, intraobserver variations in the measurement of LV dimensions, LV volumes and therefore in the computing of fractional shortening and ejection fraction. • Often these are due to variations in the frame frozen for calculations and in the delineation of the endocardial surface. • While calculating LV volumes, certain geometrical assump- tions are made about LV shape which are not always valid, particularly in a diseased heart. This often occurs in regional LV dysfunction. • Post-infarction LV remodelling increases LV sphericity and causes alteration of the normal ellipsoid shape of the left ventricle. • When assessing LV systolic function, one must allow for effects of volume loading and drug therapy. Fluid overload and antiarrhythmic drugs with negative ionotropy may further impair LV function. • In presence of mitral regurgitation (MR), ejection fraction (EF) may be normal despite reduced contractility of the LV. This is because the left atrium offers less resistance to ejection than does the aorta. • Conversely, in presence of aortic stenosis (AS), ejection fraction (EF) may be low despite normal contractility of the LV. This is because the left ventricle has to overcome a high transaortic resistance during ejection. • Therefore, after surgery (valve repair or replacement) for MR, the EF falls and after surgery for AS, the EF rises. • The calculation of cardiac output from peak aortic flow velocity by Doppler is invalid if the aortic valve is regurgitant or stenotic, because of increased aortic flow velocity. • The measurement of aortic valve diameter (D) at the aortic annulus is not only difficult but any inaccuracy is magnified, since the D value is squared.
  84. 84. Ventricular Dysfunction 75 Causes of LV Systolic Dysfunction Practically, all forms of cardiac disease ultimately culminate in LV systolic dysfunction. Prominent causes are: • Coronary artery disease – single large infarct – multiple small infarcts – triple vessel disease • LV pressure overload – systemic hypertension – aortic valve stenosis • LV volume overload – mitral regurgitation – aortic regurgitation • Left-to-right shunt – ventricular septal defect – patent ductus arteriosus • Primary myocardial disease – acute viral myocarditis – dilated cardiomyopathy Clinical Significance of LV Systolic Dysfunction • The presence of LV systolic dysfunction in any form of cardiac disease carries an adverse prognostic implication. • Patients of coronary artery disease who have LV systolic dysfunction in addition to wall motion abnormalities have a lower survival rate and poorer outcome after a revasculari- zation procedure like coronary bypass surgery.
  85. 85. Echo Made Easy76 • When a patient of hypertension with left ventricular hypertrophy develops LV systolic dysfunction, it indicates the onset of the decompensated stage of hypertensive heart disease. • Volume overloading of the left ventricle due to valvular regurgitation or a left-to-right shunt will ultimately cause LV systolic dysfunction. • Besides being a prognostic marker, onset of systolic dysfunction plays a crucial role in the timing of corrective surgery. • Presence of LV systolic dysfunction is an important criteria for the diagnosis of dilated cardiomyopathy. • Serial echocardiograms can not only assess the natural history of the disease but also the response to therapy. • Subtle abnormalities of systolic function may not be obvious at rest but brought out by exertion or stress testing. • Similarly, only minor systolic dysfunction may be observed after drug treatment of heart failure, which may have caused clinical improvement. Acute Myocarditis • Myocarditis is inflammation of the heart muscle caused by viral (Coxsackie B), bacterial (Mycoplasma) or parasitic (Lyme disease) infection. • The echo features of myocarditis are similar to those of dilated cardiomyopathy with LV systolic and diastolic dysfunc- tion and valvular regurgitation. • Abnormal LV wall motion is often global but may be segmental due to patchy inflammation of the myocardium.
  86. 86. Ventricular Dysfunction 77 • The differentiating features of myocarditis are a short history of febrile illness and an ECG showing resting tachycardia with T wave inversion. • Serial echos showing rapid improvement of LV function and regression of mitral regurgitation favor the diagnosis of myocarditis rather than dilated cardiomyopathy. LV DIASTOLIC DYSFUNCTION In recent years, LV diastolic dysfunction has attracted a great deal of attention. Diastolic dysfunction or the inability of LV to relax occurs in a variety of heart diseases and often predates the decline in LV systolic performance. A recently introduced terminology is heart failure with preserved ejection fraction or HFPEF. Normal Diastole Diastole is divided into 4 discrete periods: • Relaxation phase: AV closure to MV opening (1) • Early rapid filling: MV opening to end of filling (2) • Diastasis phase: equilibration phase (3) • Atrial systole: active atrial contraction (4) 1 and 2 comprise the phase of myocardial relaxation which is an active energy dependent process. 3 and 4 comprise the phase of myocardial distensibility which is a passive stiffness dependent process. Therefore, there are 2 patterns of diastolic dysfunction: – slow-relaxation pattern – restrictive pattern
  87. 87. Echo Made Easy78 Echo Features of LV Diastolic Dysfunction M-Mode MV Level • Motion of the anterior mitral leaflet (AML) during normal diastole has a characteristic M-shape (E-A pattern). In the presence of LV diastolic dysfunction, AML excursion is diminished, A wave is taller than the E wave and the E : A ratio is reduced. • These abnormalities occur due to stiffness of left ventricle and greater atrial contribution to ventricular filling. • These signs are neither highly sensitive nor specific for the presence of diastolic dysfunction. 2-D Echo PLAX View • 2-D echo cannot directly assess LV diastolic dysfunction. However, it can detect certain associated abnormalities such as ventricular hypertrophy, wall motion abnormality, myocardial infiltration or pericardial thickening. • Coexistent abnormalities of systolic function may be detected along with LV diastolic dysfunction. • The diastolic flow pattern from the left atrium to the left ventricle can be assessed by pulsed wave (PW) Doppler using the apical 4-chamber view with the sample volume in the mitral inflow tract. This provides a good quality spectral trace. • In the normal heart, the transmitral flow pattern (Fig. 6.6A) shows two discrete waves: E wave : passive early diastolic LV filling A wave : active late diastolic LV filling E : A ratio : greater than 1
  88. 88. Ventricular Dysfunction 79 Fig. 6.6: Various patterns of mitral diastolic inflow: A. The normal flow pattern E > A B. Slow-relaxation pattern, A > E C. Restrictive pattern, very tall E
  89. 89. Echo Made Easy80 • When myocardial relaxation is impaired due to LV hypertrophy or myocardial ischemia, the A wave is large and E wave is small, i.e. E : A ratio less than 1 (Fig. 6.6B). The deceleration time (DT) of the E wave is prolonged (> 220 msec). • In persons aged > 50 years, the E : A ratio should be less than 0.5 to qualify for diastolic dysfunction since the A wave is already dominant at this age. • This is known as the “slow-relaxation pattern” and indicates reduced LV compliance. There is increase in atrial contribution to ventricular filling. • When myocardial distensibility is impaired due to myocardial infiltration or pericardial constriction, the E wave is very tall and A wave is small (Fig. 6.6C). The deceleration time (DT) of the E wave is short (< 150 msec). • This is known as the “restrictive pattern” and indicates an elevated LV end-diastolic pressure (LVEDP). The entire ventricular inflow occurs rapidly in early diastole and the atrium cannot distend the ventricle any further. Pitfalls in the Diagnosis of LV Diastolic Dysfunction • The mitral inflow pattern of LV filling is influenced by a large number of factors besides myocardial relaxation and distensibility. • Therefore, it is inappropriate to rely only on E : A ratio as an indicator of LV diastolic dysfunction. • Factors that influence the mitral inflow pattern include: – volume loading (preload and afterload) – heart rate and cardiac rhythm
  90. 90. Ventricular Dysfunction 81 – left atrial systolic function – the phase of respiration. • Volume overloading due to mitral or aortic regurgitation attenuates the A wave since atrial contraction cannot effect forward flow if the ventricle is already maximally distended. The E wave peak is also increased. • In the presence of tachycardia, A wave is more prominent since the diastole is shortened (greater atrial contribution). When there is bradycardia, A wave is small since diastolic filling is prolonged (lesser atrial contribution). Therefore, a tall A wave carries greater significance in the presence of bradycardia. • The E : A ratio, as an indicator of diastolic dysfunction, is invalid in the presence of atrial fibrillation, complete heart block or a prolonged P-R interval. • In atrial fibrillation, there is no atrial contribution to ventricular filling. In complete heart block with A-V dissociation, the E wave and A wave occur at different times. In prolonged PR interval, the E wave and A wave occur at the same time and appear as a single wave. • In an elderly person, the A wave is dominant. If the E : A ratio is >1 or E = A with short deceleration time (DT), it indicates the presence of an elevated LV end-diastolic pressure (LVEDP). This is referred to as pseudo- normalization of MV inflow pattern. Causes of LV Diastolic Dysfunction LV diastolic dysfunction is observed in: • Advanced age (> 50 years) • Left ventricular hypertrophy • Coronary artery disease
  91. 91. Echo Made Easy82 • Restrictive cardiomyopathy • Myocardial infiltration • Pericardial constriction Clinical Significance of LV Diastolic Dysfunction • Diastolic dysfunction occurs due to increased stiffness of the LV wall, which impairs diastolic blood flow from the left atrium to the left ventricle. • The clinical features of left heart failure may occur in individuals with normal or near-normal LV systolic dysfunction as assessed by echo. These are often due to diastolic dysfunction. • Diastolic dysfunction is observed in a variety of cardiac conditions. It is more sensitive than systolic dysfunction to the effects of normal aging. • Abnormalites of diastolic function may occur in isolation, may coexist with systolic dysfunction or may be observed before major systolic impairment becomes obvious. Heart failure may be predominantly diastolic in some cases. • LV systolic and diastolic function have to be assessed separately since their causation and more importantly their treatment is considerably different. • Too simplistic a demarcation between diastolic and systolic dysfunction is often misleading. Systole and diastole are phases of a continuous cardiac cycle and interactions do occur between them. • In mild systolic dysfunction with dyskinetic areas, some regions can continue contracting in diastole leading to shortening of the time available for ventricular filling. This leads to supervening diastolic dysfunction.
  92. 92. Ventricular Dysfunction 83 • Conversely, a poorly compliant left ventricle that fails to fill adequately in diastole may cause a low stroke volume in systole. This leads to additional systolic dysfunction. • Prominent A wave can be equated to the fourth heart sound (S4) on auscultation while a prominent E wave can be equated to the third heart sound (S3). RV SYSTOLIC DYSFUNCTION Whenever echocardiography is ordered or performed, the focus is always on the left ventricle. This is because the most common cardiac conditions namely systemic hypertension, coronary artery disease and valvular pathologies affect the left ventricle. Nevertheless, the importance of the right ventricle and its role in heart disease is being increasingly recognized. Normal Indices RV internal dimension 7–23 mm RV free-wall thickness < 5 mm Echo Features of RV Dysfunction • Right ventricular size and function can be evaluated by M-mode scan from the PLAX view and 2-D echo using the apical and subcostal 4-chamber views. • RV dysfunction is associated with a dilated (> 23 mm) and hypokinetic right ventricle. • If the RV is of the same size or larger than the LV in all the echo-views, it is abnormal. An enlarged RV becomes globular and loses its normal triangular shape (Fig. 6.7). • RV free-wall thickness > 5 mm is evidence of RV hypertrophy secondary to RV pressure overload as in pulmonary hypertension or pulmonary stenosis.
  93. 93. Echo Made Easy84 • Echo may reveal the underlying cause of RV dysfunction such as a left-to-right shunt or right-sided valvular disease. • In the presence of RV failure, the right atrium is enlarged and the inferior vena cava is dilated beyond 2 cm, which fails to constrict by atleast 50 percent during inspiration (Fig. 6.8). • RV volume overload causes paradoxical motion of the interventricular septum (IVS) on M-mode scan from the parasternal long axis (PLAX) view (Fig. 6.9). Fig. 6.7: A4CH view showing dilatation of right atrium and ventricle Fig. 6.8: Dimension of the inferior vena cava (IVC): A. Normal dimension B. Dilated vena cava
  94. 94. Ventricular Dysfunction 85 Pitfalls in the Diagnosis of RV Dysfunction • Echo assessment of the RV is difficult because of heavy trabeculation, its geometrical complexity and overlap with other chambers on imaging. Moreover, the RV is located directly under the sternum. • Assessment of the RV is particularly difficult in the presence of lung hyperinflation (emphysema), pulmonary fibrosis and previous thoracic surgery. Paradoxically, study of RV function is all the more important in these patient subsets. • RV function is sensitive not only to myocardial contractility but also to loading conditions, LV contractility and septal excursion and to intrapericardial pressure. Analysis of RV function should take all these factors into account. • Even in the most experienced hands, satisfactory echo examination of the right ventricle is obtained in less than 50 percent of subjects. Causes of RV Dysfunction RV dysfunction is observed in: • Left-to-right cardiac shunt: ASD, VSD • Right-sided valvular disease: TR, PR Fig. 6.9: M-mode scan of the right ventricle showing: A. Increased dimension of the RV cavity B. Paradoxical motion of the IV septum
  95. 95. Echo Made Easy86 • Pulmonary hypertension: PRI, SEC • Right ventricular infarction: INF. MI • Right ventricular dilatation: DCMP Clinical Significance of RV Dysfunction • Assessment of RV dysfunction plays a critical role in certain congenital and acquired cardiac conditions where it is important for planning treatment, timing surgical intervention and for predicting prognosis. • In congenital heart disease such as VSD, ASD or Fallot’s tetralogy, assessment of RV function before and after surgery is a useful prognostic marker. • Similarly, timing of surgery in valvular heart disease such as MS, PS or TR is determined by the presence or absence of RV dysfunction. • The long-term prognosis of patients with chronic lung disease (COPD, ILD) depends upon RV function. RV dilatation, pulmonary hypertension and cor-pulmonale are indicators of a poor prognosis. • Following myocardial infarction, RV dysfunction may be observed in the following situations: – inferior wall infarction with RV infarction. – anterior wall infarction with acute VSD. RV infarction requires a different therapeutic approach than LV infarction. RV dysfunction due to post-MI VSD in an important cause of mortality (see Coronary Artery Disease). • RV diastolic collapse is a reliable echo parameter of cardiac tamponade (see Pericardial Diseases).
  96. 96. 7 CarCarCarCarCardiomydiomydiomydiomydiomyopopopopopathiesathiesathiesathiesathies The term cardiomyopathy means a disease of the heart muscle. In its strict sense, the term should only be applied to a condition that has no known underlying cause. In that case it known as an idiopathic cardiomyopathy. However, the term has, through popular usage, been extended to include conditions wherein there is an identifiable cause. Examples of such conditions include hypertensive, ischemic, alcoholic and diabetic cardiomyopathy. There are three main types of cardiomyopathies: • Dilated cardiomyopathy (DCMP) • Restrictive cardiomyopathy (RCMP) • Hypertrophic cardiomyopathy (HOCM) DILATED CARDIOMYOPATHY (DCMP) Echo Features of DCMP M-Mode and 2-D Echo • There is dilatation of all the four cardiac chambers particularly of the left ventricle, which thereby assumes a more globular shape (Fig. 7.1). • The left ventricular end-diastolic dimension (LVEDD) exceeds 52 mm (normal is 36 to 52 mm).
  97. 97. Echo Made Easy88 • Reduced LV wall thickness, reduced systolic thickening and reduced amplitude of wall motion are observed. The reduced LV wall motion is generalized or global rather than regional. This is known as global hypokinesia. • The LV walls are thin or there may be mild hypertrophy which is inadequate for the degree of LV dilatation. • Left atrial enlargement occurs due to stretching of the mitral annular ring which leads to functional mitral regurgitation. • There is reduced motion of the IVS and LVPW. The ventricular dimensions (LVESD and LVEDD) are increased. • Due to global hypokinesia, the systolic excursion of the interventricular septum and of the left ventricular posterior wall are reduced. • For the same reason, the left ventricular diameter in end- diastole and end-systole is increased. • Reduced fractional shortening (FS) and ejection fraction (LVEF). The ejection fraction (EF) is low but the cardiac output (CO) may be normal due to compensatory tachycardia. Fig. 7.1: A4CH view showing an enlarged and globular left ventricle
  98. 98. Cardiomyopathies 89 • Due to global hypokinesia, indices of left ventricular systolic function are reduced (see Ventricular Dysfunction). • Increased E-point septal separation (EPSS) (Fig. 7.2). It is the distance between the farthest posterior excursion of the septum and the E-point of the anterior mitral leaflet (AML). The normal EPSS does not exceed 5 mm. Note – The EPSS is reduced in hypertrophic obstructive cardio- myopathy (HOCM) due to systolic anterior motion (SAM) of anterior mitral leaflet (AML). – Measurement of EPSS lacks utility in the presence of mitral valve disease in which case free motion of the AML is already impaired. • Reduced anterior swing of aortic root during left atrial filling (normal >7 mm) • Reduced AV cusp separation in systole (normal >15 mm) with premature closure of the aortic valve (Fig. 7.3). Fig. 7.2: M-mode scan of the left ventricle showing: • increased size of left ventricular cavity • reduced movement of IVS and LVPW • increased E-point septal separation • reduced excursion of mitral leaflets

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